Winemaking is the fermentation of fruit, most commonly grapes, into a liquid. Mankind has been making wine for at least several thousand years. Winemaking or vinification consists of
- Growing the grapes,
- Harvesting the grapes,
- Crushing the grapes,
- Fermenting the crushed grapes,
- Clarifying the juice
- Aging the wine and
- Bottling or otherwise packing the wine.
Here's a bit more detail on each step, along with links and references to more information.
Growing grapes for wine
Not all grapes make good wine. The varieties selected to
become wine are chosen for many criteria, among them:
- Type of wine to be produced
- climate
- soil
- Disease resistance
Most modern grapes are grafts, the above ground portion is
selected for the properties above, and the rootstock is matched to
provide vigor and be disease resistant. Hybrids are produced when
vintners wish to combine qualities of more than one type of grape.
This UC Davis
article explains more about wine grape selection. Here are some of the most commonly grown wine varieties:
Cabernet
Franc, Cabernet Sauvignon, Carmenere, Chardonnay, Gewurztraminer,
Grenache, Malbec, Merlot, Muscat Ottonel, Nebbiolo, Pinotage, Pinot
Grigio or Gris, Pinot Noir, Riesling, Sauvignon Blanc, Semillon,
Shiraz (also called Syrah), Tempranillo, Viognier, Zinfandel.
Of course, while most wine is made from grapes, it is also made from fruit, such as peaches, blackberries, plums or even honey (which makes "Mead"). The University of Minnesota and University of California both have articles about growing wine grapes at home. Photo at right from the University of Minnesota.
Harvesting the grapes
Grapes
growing the summer months are are typically harvested in late summer
or autumn. Harvest times vary from year to year. Of course, while in
North America and Europe that means August to October, in the
Southern Hemisphere (such as Chile, Argentina, South Africa,
Australia and New Zealand), that would mean February to April. The
type of variety also affects when it is ready to be harvested.
Chardonnay and Pinot Noir are one of the first grapes picked each
year, while. Cabernet Sauvignon, Merlot and Sangiovese are among the
last grapes picked. In the Napa Valley of California, harvesting and
crushing usually starts
in mid August and ends in October.
The weather conditions can greatly affect the properties of the grapes and affect the wine. This is why vintners speak of it being a "good year" or a "bad year" or "vintage". For more detailed information about harvesting grapes, see this article.
Throughout the growing season, as the grapes mature, the growers inspect samples of the grapes to determine when the grapes have reached peak sugar content and flavor and are ready to be picked.
They use a refractometer, a
hand-held device that tests the amount of sugar in the grapes.
When the grapes are ready to be harvested, one of two methods is
used: either mechanical harvesters are used, or the grapes are
harvested by hand. Mechanical harvesters are typically used in most
medium to large vineyards,
A machine harvester sucks the grapes into a mobile field hopper.
Crushing the grapes
Some mechanical harvesters can also crush the grapes and produce must in the field while harvesting them. That helps to prevent oxidization of the juice.
The harvested grapes or must are transported to the winery - which may be on the property or completely uinconnected with the vineyard. There they are unloaded into a crusher-stemmer machine, where crushing is completed and stems are removed.
Fermenting the Grape Juice, or Must
Before fermentation is allowed to begin full force (it actually starts naturally on the grape), the nintner must decide what type of wine to make: red, white or rose. The grape skins are left in for red wines, as the pigment in the grape skins give red wine its color. The length of time the skins are left in the fermentation tank or vat determines how dark or light the color will be.
For white wines, the grape skins are usually separated from the "must" either by filters or centrifuges. And for rose', the skins stay in the tank or vat fjust long enpough to give the wine it's characteristic blush color befvore being removed.
In the fermentation process, the must is innoculated with a specific type of yeast that will feed on the sugars in the juice or must and produc e alcohol, water and carbon dioxide. Normally fermentation lasts 1 or 2 weeks. The specific strain of yeast and details of fermentation (temperature, duration, etc.) are often closely gaurded secerets.
Clarifying and Racking the wine
After fermention, the liquid is settled, clarified, and filtered. Clarification means removing solids such as dead yeast cells, tannins, proteins and impurities which could give the wine a bad taste, appearance or cause it to spoil. Wine racked (transferred or decanted) into a different containers, typically oak barrels or stainless steel tanks. Wine can also be clarified by filtration.
Fining also takes place now. That is the addition of compounds to help in the clarification, such as floculants, which cause impurities to glom together to be more easily removed by filtrationm or decantiong. The wine stays in the tanks for one to two months at 50 to 60 degrees Fahrenheit (10 to 16 degrees Celsius) for red wine, and 32 degrees Fahrenheit (0 degrees Celsius) for white wine. Another additive is sulfur dioxide (SO2) which is added during fermentation to control oxidation and act as a presevative. The use of sulfur dioxide is now commonplace.
Aging the wine
Wine is aged in tanks (usually made of stainless steel ) or large wooden vats. How long depends on many factors: white and rose wines are generally aged less than reds. Whites typically age for 1 to 4 years (but some may age even less than a year), while red wines m,ay age for 7 to 10 years or longer. The aging can occur in large stainless steel tanks in above ground buildings (typical in larger wineries), or, in wooden barrels in wine cellars (typical smaller traditional wineries, and also typically premium wines). In both cases, temperature-control, either using AC/heating in the building, builting into the tanks or naturally in the cellar or "cave" is important to quality.
Still or Sparkling wine?
We haven't mentioned it thus far by still wine (wine without without carbonation) and sparkling wine (with bubbles or carbonation, like Champagne) use different methods. Carbonation can be added from perssurized CO2 injected into the bottles, or can occur naturally in each sealed bottle. When natural fermentation is used, it is called a "secondary" fermentation.
Bottling
With the introduction of boxed wines, we should really call this "packagin". Wineries may have automated bottling machines or do it manually. Corks used to be almost exclusively made or cork from Portugal, but plastic corks have taken over market share, as they have demonstrated to be more reliable and can be made to meet specific breathing properties. Some corks are even made of a special oak.
Corks are covered with a wrapper of aluminum foil or plastic.
Lead foil is no longer used for obvious health reasons. Some wines
use a screw cap, which had long been associated with cheaper winesbut
have become more mainstream. . The corks and screw caps keep the
air from spoiling the wine. Wine is usually shipped in wooden
crates, though cheaper wines may be packaged in cardboard.
